1. Field of the Invention
This invention relates to telephone paystations, and more particularly to a coin escrow mechanism for temporarily storing and then either refunding or collecting coin deposits.
2. Background Art
Coin escrow mechanisms or coin relay hopper mechanisms have existed since coin telephones have existed. AT&T, GTE, and Northern Telecom have produced various designs for years for both the older three slot and more recent single slot coin telephones.
Early designs were predominantly of a double coil variety up until about 1960 when AT&T and then others introduced a single coil design with a round cross section tubular hopper similar if not identical with what AT&T uses today. Early designs did not contend with a multiple of large coin deposits, as typically a local telephone call was a nickel or dime. The AT&T hopper with a trap door and directing vane was probably a response to higher deposit requirements. Its storage capacity with a high degree of freedom from coin jams is about $3.00.
In approximately 1972, GTE introduced the single slot coin telephone in response to a previously introduced single slot coin telephone by AT&T. As a part of this program, a new design coin relay hopper was introduced. Rather than a round cross section tubular hopper, a rectangular cross section tubular hopper with two trap doors in a "V" notch configuration with a single central pivot point was used for holding and directing coins. Rather than the coin stack being controlled as in the AT&T configuration, the coins were allowed to stack at random. Its storage capacity with a high degree of freedom from coin jams was about $4.00.
Other design coin escrow mechanisms have also been introduced to the market, particularly from foreign sources in recent years. A predominant type is a rectangular cross section hopper with two trap doors in a "V" notch configuration with double outside pivot points on each door. Two coils are generally used for activation. Although these units have not been tested for capacity, they have often failed due to large current requirements for operation.
For a general understanding of the coin holder relay operation, reference is made to U.S. Pat. Nos. 3,759,440, 3,759,441 and 4,386,690, all of which are assigned to the same assignee as the present application.
In operation, the first coin exits the coin rejector and strikes the paddle of the trigger switch actuator to cause rotation and unlatch the first coin switch to the operate position. Subsequent coin deposits may further rotate the trigger switch actuator, but will not effect the first coin switch. Large coin deposits will fully rotate the actuator where the paddle arm slot is blocked and the paddle portion is completely out of the way in a pocket of the hopper making the trigger effectively transparent to coins. Coins are held in place by their respective collect and refund latches.
When a telephone call is completed or abandoned, the coins are collected or refunded, respectively. Voltage polarity as determined by the telephone operating company central office or other controlling circuits (positive for collect, negative for refund) is applied to the relay coil leads.
A magnetic field is generated by the relay coil which influences the selector card by virtue of its containing a permanent magnet to either rotate clockwise for collect, counter clockwise for refund. The magnetic field also subsequently causes the armature of the relay to close.
The rocker arm which is attached to the armature pushes the selector card down to operate the proper latch.
The latch selected is dependent upon which direction the selector card is rotated, i.e., the polarity of the voltage. Upon operation of a latch, the corresponding trap door will open and the coins will be released down either the collect or refund chute.
When the armature operates, it pushes the switch card which operates the entire contact spring pile up. The movement of the first coin switch will release the entire trigger switch actuator to return to the home position. It is held in the home position by a torsion spring.
When voltage to the relay is removed, the armature is returned to the home position by the margining spring and the timing spring. With the armature the rocker arm rotates and drives the selector card to its home position. The selector card in turn drives the operated latch to its non operate position which returns the door.
As the cost of telephone calls increases, the average amount held in escrow in the coin relay hopper and then either collected or refunded is increasing. If the telephone company has a maximum amount allowed in escrow, this maximum will be affected more and more often. If multiple collections are used, they will occur on a higher percentage of telephone calls.
Because test results indicate failure rates at 1% and 2% even at moderate coin loads, the coin relay hopper maintenance problems must be growing. What is necessary then is not to collect larger coin loads but to collect moderate coin loads more reliably.
Multiple collections at lower levels is not the answer. This approach requires increased supervision and once partial deposits are collected they cannot be refunded.
Coin capacity is the dollar value of the coins that can be collected or refunded on one operation of the coin relay hopper mechanism that meet electrical operate and reliability requirements. Generally, it is equal to the total value of the telephone call but as previously stated this may not be true.
In testing, the coinage used is an even mixture of nickels, dimes and quarters, as this is considered "worst case" conditions. Generally, capacity is increased as the percentage of dimes and quarters is increased. Electrical operate conditions used in testing are also "worst case", just slightly above the margining limits of the relay mechanism.
Failure can occur in five ways:
The coin relay does not operate at the minimum operate criteria or test criteria at the coin load specified. It does not have enough power to overcome the frictional forces of mechanism.
The hopper mechanism false discharges during the deposit of coins before normal energy is applied.
The relay operates properly but the coin load split between collect and refund.
The relay operates properly but the coin load jams and fails either partially or wholly to discharge down the collect or refund tube.
The coin load overflows and backs up into the previous subassembly.
In order to understand the coin capacity improvements of the invention, the following detailed discussion of some existing hopper assemblies and coin jamming modes is required.
Usually, the main body of the hopper assembly is a casting assembly which has three distinct areas: 1) the hopper or storage area being in effect a rectangular cross section tube, 2) the collect channel being a smaller rectangular tube angling off to the right at 45 degrees, and 3) the refund channel being a smaller rectangular tube angling off to the left at 45 degrees. The front and back of all tubes are in the same plane, the unit being of uniform width. The unit is essentially symmetrical when the storage area is split down the middle. All tubes are open ended.
The left and right hand sides of the storage area intersect the tops of refund and collect tubes, respectively, and create what we shall designate as the refund and collect corners.
Two trap doors, a refund trap door and collect trap door hinge on the same shaft located at the theoretical intersection of the bases of the refund and collect tubes. When closed, a door is perpendicular to the base of its tube, closing that tube by extending from the base to the top of the tube. When the open door rotates 90 degrees, it becomes flush with the base of its tube, while the opposite door remains in its operated position keeping its tube closed.
As the hopper assembly is symmetrical, our discussion will continue covering the right or collect side only, with the understanding that all arguments apply to the left or refund side also. The collect door configuration is that of a rectangular flat plate hinged on one end and latch operated. Along the edges of the plate that interfaces with the front and the back surfaces of the collect tube are three projecting fingers equally spaced. Corresponding to each of these fingers are grooves in the walls of the collect tube. Between the grooves are land areas flush with the front and backs of the collect tube. This finger and groove arrangement has the purpose of keeping thin coins, namely dimes, from sliding down past the edge of the door and the front and back of the tube. The grooves form 90 degree arcs with respect to the axis of rotation of the door.
The top of the collect door extends to the top of the collect tube to a position slightly below and the right of the collect corner. This is beneficial to the operation of the total coin relay hopper assembly as the tip of the collect door is protected from the weight of heavy coin loads. As the latch that operates the door is at a severe mechanical disadvantage to the door, these heavy loads could mean a non-operate condition when limited power is available.
In theory, coins stack at random in this type of hopper design. In practice, they follow patterns. One such pattern is where coins stack with their sides parallel to the refund door with their edges resting against the collect door. The axis of the stack is 45 degrees from vertical. When coin loads are large, this stack can pile up to the collect corner. Sometimes the stack is not perfect, coins partially extend into the stack. This will give the stack a "wedge" or tipped appearance. The part of the stack touching the collect door and under the collect corner is shorter than the part of the stack that extends away from the door. When the collect door opens, this "wedge" formation jams against the collect corner.
A variation of the above is where the pattern has a parquet appearance and the direction of the axis of one smaller interspaced stack is 90 degrees from the axis of the main stack. A "wedge" effect can also exist with this type of pattern.
In all of the above patterns coins slide or tumble rather than roll down the collect tube.
Another pattern is where a few coins turn vertical and rest against the side of the hopper. In this orientation it would appear that they would roll down the collect tube. The majority of the other coins would be in the center of the hopper in combinations of stacks and would be in the sliding or tumbling orientation. In these patterns a combination of two or more coin thickness and one quarter diameter can span or slightly exceed the width of the hopper or collect tube, thus the "fit" can become tight enough to jam. This pattern is referred to as the "T-bone" pattern or jam. It can have a configuration of an "I" when vertical coins are on opposite sides of the hopper.
The coin relay assembly needs to be field removable from the hopper assembly, therefore its mounting features need to be designed for quick change. Also, the paddle portion of the trigger switch actuator needs to be capable of being positioned into and out of the hopper without its being disassembled from the coin relay assembly.
On existing designs this is accomplished by a similar mounting arrangement. The primary task in relay removal is to disassemble two large screws at the bottom of the relay which face left center and right center. These screws go thru holes in the rather large left and right relay mounting arms which extend from the bottom of the hopper. There are mating tapped holes in the core bracket of the coin relay assembly into which these screws are driven. To complete dismounting there are one or two screws at the top of the relay that need to be removed. The mounting arm feature on existing hoppers are subject to warpage and critical dimensions are difficult to control.
The first coin switch on coin relay hopper assemblies is operated when a coin is deposited. One of the contact springs of this assembly interfaces with the cam portion of the activator. Adjustment of this spring at times is necessary to meet operate criteria.
In some designs one side of the adjustors access and vision is blocked by the arm of the trigger switch actuator that connects the shaft portion with the cam portion. This makes adjustment more difficult.